This invention generally relates to methods and systems for processing cheese products, and more specifically, to controlling the moisture content of cheese products as those products are being processed.
Processed cheese products typically are prepared by forming a blend of one or more comminuted natural cheeses, together with various additives such as whey or emulsifying salts. The processed cheese products are produced by heating, melting, and mixing the cheese blend to form a homogenous emulsified molten mass, followed by cooling and solidification of the molten mass. Such processing, for example, with emulsifying salts such as sodium phosphate and/or sodium citrate in amounts of 2-3 wt. % permits manufacture of soft-bodied, easily meltable processed cheeses and processed cheese foods.
Because of their molten, easily handled form, processed cheese products may be readily packaged to provide convenient consumer products. Packaging may take any one of a number of forms such as hot packing in a plastic film tube that is cross-sealed and cut to provide individually wrapped slices. The molten process cheese product may also be formed into slices by distributing a thin layer of the product upon the surface of a cooled rotating chill roll, solidifying that layer into a sheet and removing the sheet from the roll. The sheet is then cut into strips and subsequently into slices, followed by packaging of the sliced processed cheese product.
Various prior art methods and systems for processing cheese or cheese products are disclosed, for example, in U.S. Pat. Nos. 5,165,945, 5,104,675, and 4,689,234. U.S. Pat. No. 5,165,945 discloses a process in which milk clotting enzymes are introduced into a feed stock containing cheese ingredients, and the enzyme-treated feed stock is heated to produce a desired body, texture, and solids level. U.S. Pat. No. 5,104,675 discloses a process for preparing cheese products on a continuous in-line basis by providing a uniform blend of specific types of natural mozzarella and cheddar cheeses with limited amounts of sodium citrate. U.S. Pat. No. 4,689,234 discloses a process for producing cheese, in which milk is initially concentrated by ultrafiltration and diafiltration to obtain a desired buffer capacity to lactose ratio in the retentate. A lactic acid producing starter culture is then inoculated into the retentate, and the retentate is then fermented to obtain a desired final pH.
The moisture content of the final cheese product is a key parameter, having a significant effect on the quality and cost of the product. Controlling that moisture content is complicated by the fact that, conventionally, water is added to and removed from the cheese blend at various points in the manufacturing process, and the amounts of water that are added to and removed from the cheese blend at these points are not always precisely controlled.
For instance, in a common process, water is added while the comminuted natural cheeses and the additives are blended. The blended mixture is cooked to a target temperature by the direct injection of steam either continuously into a pipework or batchwise into a vessel containing the mixture. After a product-specific holding time at the target temperature, the cooked cheese product is cooled by the direct flashing of steam from the cheese product. The amount of water that is added to the cheese product during the blending step can be controlled relatively precisely. However, similar precise controls cannot be exercised over the amounts of water that are absorbed by and subsequently drawn out from the cheese product during the above-mentioned cooking and cooling steps.
With prior art processes, the moisture content of the final product can be controlled to within a range of plus or minus 2% of a target value, depending on the product type, the manufacturing equipment, the raw material, and other factors; and generally, these processes produce excellent products. Nevertheless, it is believed that the cost of the processes can be reduced and the uniformity of the product quality can be improved by narrowing the above-mentioned moisture range.